Sheet materials, such as tissue paper, are often interfolded into stacks or clips and then placed into a dispenser such that, upon removal of one sheet, a subsequent sheet is partially dispensed having an exposed portion that extends from the dispenser's opening. This method of pop-up sheet dispensing is convenient for many applications, since the next sheet is readily presented for quick access.
Three common dispensing problems often result during pop-up dispensing. The first problem can be sheet tears for the dispensed sheets; especially, from a full or nearly full dispenser. The second problem can be fallback where the next sheet in the dispenser fails to be partially withdrawn through the dispensing opening upon removal of the preceding sheet. Fallback can occur because there is insufficient interfolding of the sheets to create enough interlayer sheet-to-sheet friction to partially withdraw the next sheet. The third problem, multiple dispensing, happens when withdrawing one sheet causes one or more additional sheets to be withdrawn unintentionally. Multiple dispensing can occur because there is too much interfolding of the sheets creating more interlayer friction than desired, causing additional sheets to be withdrawn in a chaining or linking effect.
Conventional dispensers or cartons are available in a variety of designs and shapes, but they can generally be classified as either one of two basic styles. One style is the flat carton and the other is the upright or boutique carton. In the flat style cartons, the sheets are laid flat in the bottom of the carton and are withdrawn from an opening in the top of the carton or through an opening in the top which partially extends down the front sidewall. The sheets within the carton may be interfolded for pop-up dispensing or merely laid on top of each other for reach-in dispensing.
In the other style carton, the sheets are packaged in an upright or boutique type dispenser by folding the stack. The upright dispenser can be preferred since it has a smaller footprint than flat dispensers. To dispense the sheets from an upright dispenser, the sheet material is typically interfolded into a stack or clip of tissues and then the clip is folded symmetrically in half about a transverse central axis of the clip to form a U-shaped folded clip that is loaded into the dispenser. The U-shaped clip is loaded into the dispenser such that the radius of the U is beneath the dispensing window located in the dispenser's top.
Loading an upright dispenser with the U-shaped clip can cause the first few sheets to be difficult to remove and/or tear, especially as the number of sheets in the dispenser is increased or as the bulk/thickness or number of plies of the sheet material is increased. The sheets can be pushed tightly against the opposing vertical walls of the upright dispenser after the folded clip is placed in the dispenser since the clip tends to spring back into an uncompressed state. This can lead to tearing of the sheet material as the sheets are dispensed. This is particularly true for the initial sheets dispensed after the carton is opened. The problem is often lessened as the sheets within the carton are used up and the compression of the clip is reduced.
Increasing the overall size of the upright dispenser or reducing the number of sheets in the clip are both viewed as unacceptable solutions. The current size of the upright dispenser has become standardized, and many people have decorative covers designed to fit over the size of an upright dispenser. Reducing the number of sheets will impact the perceived value by a purchaser who expects to receive a significant number of sheets such that the product will last a long time in use.
One approach to solving this problem is to add a dynamic friction reducing material to the inside of the carton as disclosed in U.S. Pat. No. 6,672,475, entitled Dispensing Carton for Paper Sheet Products that issued on Jan. 6, 2004, to Ho et al. This approach tries to reduce the friction between the clip and the inside of the dispenser by extending the poly film dispensing window on the inside of the dispenser. However, simply reducing the friction of the clip's outer sheet with the carton will not guarantee that the initial sheets will not tear. In the U-shaped clip there is present a substantial amount of interlayer sheet-to-sheet friction between the interfolded sheets. Additionally, adding the dynamic friction reducing material to the dispenser increases the incremental cost of the dispenser, which cannot always be passed on by the manufacturer as a cost increase.
Another approach to solving this problem in a flat dispenser containing wet sheets is disclosed in U.S. Pat. No. 6,543,643, entitled Sheet Package that issued on Apr. 8, 2003, to Iida et al. This approach reduces the folded width of the upper layer sheets in the stack as compared to the lower layer sheets such that the initial sheets are easier to remove through the dispensing opening. While this approach may be useful for flat dispensers containing wet sheets, the approach can be unsuitable for upright dispensers. By reducing the folded width of the sheets in the upper layer, the overall height of the stack is increased. This occurs because if the folded width is reduced for a sheet having the same initial size, then the corresponding folded height must also be increased. When the now taller stack is folded into a U-shape and then placed into an upright dispenser, the initial clip compression is actually increased from the wider stack being compressed more by the dispenser resulting in more sheet tears. This is the exact opposite of the intended result. If the taller stack is used in a flat dispenser, the size of the dispenser must be increased to accommodate the taller stack, or fewer sheets must be placed into the stack to fit the currently existing dispenser.
Thus, what is needed is an interfolded stack that can dispense more sheets from the same sized dispenser while still achieving acceptable dispensing with a minimum of the above discussed problems. Alternatively, what is needed is an interfolded stack that can dispense the same number of sheets from the same sized dispenser with a reduction in the above discussed dispensing problems. Alternatively, an interfolded stack that contains more sheets and dispenses them with a reduction in dispensing problems from the same sized dispenser is also needed.